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i <br /> 10 June 1999 <br /> AGE-NC Project No 97-0290 <br /> Page 8 of 26 <br /> The vacuum applied at V W 1 B and the induced vacuums at SW 1 B and SW2B were graphed versus <br /> distance utilizing a best fit line on a semi-loganthmic scale (See Figure 10) Based on the induced <br /> vacuum potentials measured from SW 1 B and SW2B, a theoretical radius of influence in soils at the <br /> I <br /> site for an applied vacuum of 30 to 40 inches of water is 34 feet for an induced vacuum of 0 1 inches <br /> of water <br />' Data from MWl, MW2 and VW1C were also graphed versus distance A much larger than expected <br /> vacuum potential was detected in MW The vacuum measured in MW2, screened from 40 to 60 feet <br /> bsg was similar to that observed at SW2B, screened at 33 feet The extraction well (VW1B) is <br /> screened from 29 to 37 feet bsg <br /> 45 ANALYTICAL RESULTS OF EXTRACTED SOIL GAS SAMPLES <br /> I During the SVE pilot test, TPH-g was detected in extracted soil gas samples collected from VW 1 B <br /> at concentrations ranging from 72,000 micrograms per later (Acg/L) to 120,000 /.cg/L TPH-g was <br /> detected in the sample collected from VW1A at a concentration of 59,000 µg/L <br /> BTEX compounds were detected in soil gas samples collected from VW 1 B at concentrations up to <br /> 2,900µg/L Benzene was detected in the soil gas sample collected from VW1A at a concentration <br /> I of 5,000/.,4g/L MTBE was not detected in any of the soil gas samples as analyzed by EPA Method <br /> 8020 Analytical results of soil gas samples are summarized in Table 7 The laboratory report <br /> (McCampbell Analytical Inc Lab I D 10954 to 10958) and chain-of-custody forms are presented <br />' in Appendix B <br />' 5.0. ASSESSMENT OF HYDROCARBON-IMPACTED SOIL AND GROUND WATER <br />' Previous assessment activities were summarized above in Section 2 3 The highest concentrations <br /> of petroleum hydrocarbons in soil were detected near the southeast portion of the site at depth <br /> intervals of 15 to 25 feet bsg and 35 to 50 feet bsg Lower concentrations of hydrocarbons were <br />' detected in borings B4, MW4 and B6, surrounding the southeast portion of the site, at depths of 35 <br /> to 60 feet bsg, corresponding to historical fluctuations in ground water levels Impacted soil at depth <br /> appears to be concentrated in a silt and clay layer between approximately 40 to 47 feet bsg The <br />' approximate extent of impacted soil is illustrated on Figures 3, 4 and 5 Lines of cross section are <br /> shown on Figure 3 <br />' The highest concentrations of petroleum hydrocarbons in ground water were detected in samples <br /> . collected from MW2, P2, P3, B4 and B6 Petroleum hydrocarbons were not detected in water <br />' samples collected from MW6 and MW7 The approximate lateral extent of impacted ground water <br /> �� Arhsanced Geol;miron mental,Inc <br />